The disclosure of U.S. Pat. No. 5,182,166 issued Jan. 26, 1993 to Ralph A. Burton and Ralph G. Burton for xe2x80x9cWear-Resistant Composite Structure of Vitreous Carbon Containing Convoluted Fibersxe2x80x9d is hereby incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates generally to reinforced vitreous carbon composites and methods of making and using the same.
2. Description of the Related Art
U.S. Pat. No. 5,182,166 issued Jan. 26, 1993 describes a wear-resistant vitreous carbon composite containing convoluted reinforcement fibers, and a method of making and using same.
The composite and methodology of U.S. Pat. No. 5,182,166 resolve cracking issues involved in pyrolyzed glassy carbon composites of the prior art, by the provision of convoluted fibers producing a highly improved crack-resistant character to the composite mateial. Further, from the standpoint of tribological properties, the vitreous carbon composites of U.S. Pat. No. 5,182,166 provide markedly improved wear-resistance, as compared with pyrolyzed glassy carbon composite materials of the prior art.
The invention herein disclosed embodies various improvements in the composites technology disclosed in such U.S. Pat. No. 5,182,166.
In the polymerization of liquid-phase monomeric or oligomeric organic materials to provide a polymer that is pyrolizable to form vitreous carbon as a continuous phase material for a reinforced vitreous composite, the polymerization reaction involves (1)joining of molecules of the monomer and/or oligomer into multi-molecule chains and (2) cross-linking of these chains by chemical bonds. This process is exothermic and the released heat of polymerization is substantially trapped in the polymerizing liquid resin, since the liquid resin is a poor conductor of heat. Such heat of polymerization reaction is sufficient to bring the resin to a temperature above its boiling point, and even cup-full amounts will foam and fume.
In consequence, the composite formed from such a resin will correspondingly contain foaming and fuming defects in the structure of the polymerized material, which then in subsequence pyrolysis will be retained as material defects of the continuous phase material. The product composite then is non-homogeneous and non-isotropic in character, containing gross voids or pores, and cannot be used in applications where uniformity of the morphology and of the structural/performance properties of the composite material are required.
Conversely, when the reaction rate of the polymerization is low, as a result of low temperature and/or low concentrations of polymerization catalyst, the product xe2x80x9cgreen bodyxe2x80x9d material is leathery in texture and does not yield good carbon bodies on subsequent firing for pyrolysis of the polymer.
These problems are resolved by the composite material herein disclosed and the process herein disclosed of making same.
In one aspect, the present invention relates to a metal-reinforced vitreous carbon composite including a metal fiber discontinuous phase in a continuous phase vitreous carbon that is essentially free of foam and fume indicia, wherein the composite is of a three dimensional character having each of its dimensions being at least 25 millimeters.
Another aspect of the invention relates to a metal-reinforced carbon composite including a metal fiber discontinuous phase in a continuous phase vitreous carbon that has been formed by polymerization of a continuous phase precursor material comprising furfuryl alcohol monomer and/or oligomer, followed by pyrolysis of the polymerized material, wherein the polymerization is carried out under polymerization conditions below the boiling point of the precursor material, and wherein the composite is of a three dimensional character having each of its dimensions being at least 25 millimeters.
A still further aspect of the invention relates to a metal-reinforced vitreous carbon composite including a metal fiber discontinuous phase in a continuous phase pyrolyzed poly(furfuryl alcohol) vitreous carbon material wherein the composite is of a three dimensional character with each of its dimensions being at least 25 millimeters and wherein the composite is substantially completely void-free in character.
A further aspect of the invention relates to a vitreous carbon composite including a continuous phase of pyrolyzed poly(furfuryl alcohol) vitreous carbon material polymerized and pyrolyzed about a discontinuous silicon bronze material to form a composite structure including a carbocupric reaction product as a third phase material between the vitreous carbon continous phase and the discontinuous silicon bronze material.
In another aspect, the invention relates to a metal-reinforced vitreous carbon composite including a metal fiber first discontinuous phase and a thermally non-conductive second discontinuous phase in a continuous phase pyrolyzed poly(furfuryl alcohol) vitreous carbon material.
A further aspect of the invention relates to a metal-reinforced vitreous carbon composite including a needle-punched metal wool discontinuous phase in a continuous phase pyrolyzed poly(furfuryl alcohol) vitreous carbon material.
The invention in other aspects relates to products comprising a metal-reinforced vitreous carbon composite of the invention, such products including third rail current collectors, pantograph assembly, trolley shoes, electrical brushes, seals, bearings, therapeutic structures for implantation in an animal body, e.g., human or other mamallian body, such as a joint replacement structure, etc.
Another aspect of the invention relates to a multilayer laminate material comprising at least one layer of a vitreous carbon composite including a metal fiber discontinuous phase in a continuous phase pyrolyzed poly(furfuryl alcohol) vitreous carbon.
A further aspect of the invention relates to a poly(furfuryl alcohol) film, characterized by a degree of polymerization imparting to the film a flexible character.
A still further aspect of the invention relates to a metal-reinforced poly(furfuryl alcohol) composite green body including a metal fiber discontinuous phase wherein the composite is of a three dimensional character with each of its dimensions being at least 25 millimeters and wherein the composite is substantially completely void-free in character.
In one method aspect, the invention relates to a process for making a metal-reinforced vitreous carbon composite material, comprising the steps of:
providing a mold including therein a mold cavity and wall structure bounding the mold cavity, wherein the wall structure is formed of a thermally conductive material at a wall thickness providing a substantial thermal heat sink for heat of polymerization of a material polymerized in the mold cavity;
disposing in said mold cavity a metal fiber matrix defining a three-dimensional structure including void space therein;
compressing the three-dimensional structure in the mold, e.g., to laterally conform the structure to the wall structure of the mold cavity while retaining void space therein;
partially polymerizing exterior to the mold cavity a continuous phase precursor material comprising (i) a poly(furfuryl alcohol) monomer and/or oligomer and (ii) a polymerization catalyst, to conduct an exothermic polymerization reaction generating a heat of polymerization;
removing from the partially polymerized precursor material at least part of the heat of polymerization therefrom exterior of the mold cavity;
introducing the partially polymerized precursor material, subsequent to removal of at least part of the heat of polymerization therefrom, into the mold cavity; compressively consolidating the partially polymerized precursor material with the three-dimensional structure in the mold cavity under polymerization conditions to form a metal-reinforced polymer composite material; and
subjecting the metal-reinforced polymer composite material to pyrolysis conditions effective to pyrolyze the polymer in the composite material, to yield the metal-reinforced vitreous carbon composite material.
Another aspect of the invention relates to a process for forming a metal-reinforced vitreous carbon composite comprising:
providing a metal fiber discontinuous phase;
impregnating the metal fiber discontinuous phase with a precursor including (i) furfuryl alcohol monomer and/or oligomer and (ii) a polymerization catalyst;
polymerizing the precursor;
removing exothermic heat of polymerization from the precursor to maintain temperature of the precursor in a temperature range of from about 40xc2x0 C. to about 100xc2x0 C., and gel time of the precursor in a range of from about 2 to 30 minutes; and
pyrolyzing polymerized precursor to yield the metal-reinforced vitreous carbon composite.
Other aspects and features will be more fully apparent from the ensuing disclosure and appended claims.